Web Servers and Web Clients

A Web server is a computer that delivers (or serves up) Web pages. Web servers listen on port 80, fetching requested HTML pages and sending them to browsers. You can turn any computer into a Web server by installing server software and connecting the machine to the Internet, but you need to consider the operating system and Web server program you'll use to serve your Web site. Microsoft pushes Internet Information Services (IIS).

IIS enables you to set a maximum connection limit on your Web server based on available bandwidth and memory. This enables you to protect your network against an overwhelming number of requests due to a particularly popular page or a type of malicious attack called a denial of service (DoS) attack.

Microsoft builds an artificial 20-connection limit into Windows 2000 Professional, Windows XP, and Windows Vista so you should only run IIS on Server versions of Windows (unless you don't expect too many people to visit your Web site at one time).

UNIX/Linux-based operating systems run Apache HTTP Server. As of this writing, Apache serves well over 50 percent of the Web sites on the Internet. Apache is incredibly popular, runs on multiple operating systems (including Windows), and, best of all, is free! Apache is nothing more than an executable program and a bunch of text files, so it isn't much to look at. To ease configuration, most Web administrators use addon graphical user interfaces (GUIs) such as Webmin that make administering Apache a breeze.

IIS and Apache are by far the most common Web servers used on the Internet. In third place is Google Web Server (GWS). GWS, used only by Google's servers, has about 5 percent of the total Web server market! After those three there are literally hundreds of other Web servers, but outside of small personal Web sites you'll rarely see them.

NOTE In early 2009, China released numbers for a Chinese-only Web server called QZHTTP server and, as with anything to do with China and population, the numbers for hosted sites are staggeringly large. If accurate and sustained, QZHTTP would supplant GWS as the third most popular Web server software.

Web clients are the programs used to surf the Web. A client program (a Web browser) reads Web pages supplied by the Web server. Most browsers handle multiple functions, from reading HTML documents to offering FTP services, and even serving as an e-mail or newsgroup reader. (You'll learn all about these functions later in the tutorial.) The most popular Web browsers are Microsoft Internet Explorer, Mozilla Firefox, Apple Safari, Opera, and Google Chrome.

NOTE Most Windows users just use Internet Explorer since it comes on Windows by default.